Method of Servicing a Power Generator

ABSTRACT

A method of servicing a stator frame of a power generator. The method includes removing a first stator core from a main housing of the stator frame, removing a plurality of first dove-tail shaped keybars that extend axially within and are coupled to a main support structure forming part of the main housing, and installing a plurality of second keybars in the main support structure. The second keybars are adapted to support a second stator core. Each of the second keybars has a generally rounded engagement surface and the second stator core includes recesses with shapes corresponding to the generally rounded engagement surfaces of the second keybars such that the second stator core can be securely supported in the main support structure by the second keybars.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/037,887, entitled CORE TO FRAME ATTACHMENT IN A UNIT WITHOUTBUILDING BOLTS, filed Mar. 19, 2008, the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to power generators, and moreparticularly, to a method of servicing stator frames in powergenerators.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,875,540, the entire disclosure of which is incorporatedby reference herein, discloses a process for forming a stator core in astator frame. The process involves forming a plurality of core modulesor donuts, each of which comprises a plurality of stator core ringslaminated together. The stator frame is placed in an upright position. Apredefined number of the core modules are then lowered into the uprightstator frame. For a power generator which has been in operation for sometime and is in need of a new stator core, turning its stator frameupright to receive a new stator core can be very difficult.

U.S. Pat. Nos. 7,302,754; 7,353,586; and 7,395,594, the entiredisclosures of which are incorporated by reference herein, are directedat installing stator cores into stator frames without placing the statorframe in an upright position. U.S. Pat. No. 7,202,587, the entiredisclosure of which is also incorporated by reference herein, disclosesmounting stator core donuts having enlarged grooves in a stator frameusing wedges that disperse forces to the donuts in a circumferentialmanner. The enlarged grooves make installing the donuts less difficult,while the wedges ensure a tight fit of the laminations within the statorframe.

FIG. 1 illustrates a known stator frame 10 for a power generator. Thestator frame 10 comprises a main housing 11 for supporting a statorcore, not shown in FIG. 1. The main housing 11 comprises an outerstructure 13 and a main support structure 15 coupled to the outerstructure 13. The main support structure 15 comprising a plurality ofstator bore or support rings 18 coupled to the outer structure 13 and aplurality of frame beams 16 coupled to the stator bore rings 18. Themain housing 11 further comprises a plurality of dove-tail shapedbuilding bolts or keybars 12 coupled to the frame beams 16. The statorcore, not shown in FIG. 1, is supported in the stator frame 10 via thekeybars 12.

FIG. 2 illustrates a stator core lamination or donut 14 comprising aplurality of stator core rings (also referred to as laminations)laminated or otherwise coupled together and configured to be supportedon the keybars 12 illustrated in FIG. 1. It is noted that a plurality ofthe stator core donuts 14 are stacked together within the stator frame10 to form the stator core. Referring now to FIG. 2, each stator coredonut 14 includes a plurality of slots or grooves 20 (see FIG. 3) alongits outer periphery to receive the keybars 12. The grooves 20 have adove-tail shape corresponding to the shape of the keybars 12 to ensure asecure and tight fit within the stator frame 10, as more clearly shownin FIG. 3. It is noted that small radial gaps 21 are formed between theperiphery of each stator core donut 14 and the inner diameter of thesupport rings 18, as shown in FIG. 2. It is also noted that one or moremounting assist structures 23A, 23B, 23C may be disposed in each groove20 between the stator core donut 14 and the corresponding keybar 12. Themounting assist structures 23A, 23B, 23C assist in securing a tight fitbetween the stator core donut 14 and the keybars 12.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a method ofservicing a stator frame of a power generator is provided. The methodcomprises removing a first stator core from a main housing of the statorframe, removing a plurality of first dove-tail shaped keybars thatextend axially within and are coupled to a main support structureforming part of the main housing, and installing a plurality of secondkeybars in the main support structure. The second keybars are adapted tosupport a second stator core. Each of the second keybars has a generallyrounded engagement surface and the second stator core includes recesseswith shapes corresponding to the generally rounded engagement surfacesof the second keybars such that the second stator core can be securelysupported by the main support structure via the second keybars.

The main support structure may comprise a plurality of stator bore ringsand a plurality of frame beams, wherein the second keybars are coupledto the frame beams.

Installing a plurality of second keybars in the main support structuremay comprise bolting the second keybars to the frame beams.

Bolting the second keybars to the frame beams may comprise installingbolts into counter-bored holes until end portions of the bolts areinserted past a radially inner surface of the second keybars.

The method may further comprise installing the second stator core ontothe second keybars.

The method may further comprise servicing the frame beams such that thesecond stator core can be more easily axially slid onto the secondkeybars without the second stator core contacting the frame beams.

Servicing the frame beams may comprise removing radially inner corneredges of the frame beams to create a radial clearance for a radial outeredge of the second stator core.

A portable milling machine may be utilized to remove the radially innercorner edges of the frame beams.

In accordance with a second aspect of the present invention, a kit forservicing a stator frame of a power generator is provided, wherein thestator frame includes dove-tail keybars installed therein supporting afirst stator core within a main support structure of a main housing. Thekit comprises a plurality of second keybars and fasteners to couple thesecond keybars to the main support structure of the main housing. Eachof the second keybars has a generally rounded engagement surface and isadapted to replace the dove-tail shaped keybars installed in the mainsupport structure. The second keybars are adapted to support a secondstator core in the main support structure. The second stator coreincludes recesses with shapes corresponding to the generally roundedengagement surfaces of the second keybars.

The main support structure may comprise a plurality of stator bore ringsand a plurality of frame beams, wherein the second keybars are coupledto the frame beams with the fasteners.

The fasteners may comprise bolts, which may be installed throughcounter-bored holes in the second keybars.

End portions of the second keybars may extend further radially inwardlythan a radial end of the bolts.

The kit may further comprise a portable milling machine for removingradially inner corner edges of the frame beams to create a radialclearance for a radial outer edge of the second stator core.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a cut-away perspective view of a prior art generator frameincluding an annular array of dove-tail shaped keybars;

FIG. 2 is a cross sectional view of an inner portion of the prior artgenerator frame illustrated in FIG. 1 and further including a prior artstator core donut;

FIG. 3 is an enlarged cross sectional view of a portion of the prior artgenerator frame and a portion of the stator core donut illustrated inFIG. 2;

FIG. 4 is a cross sectional view of a portion of a generator frameincluding a replacement donut after the generator frame has beenserviced according to embodiments of the invention;

FIG. 5 is an enlarged cross sectional view of a portion of thereplacement donut illustrated in FIG. 4 and a replacement keybarinstalled in the generator frame illustrated in FIG. 4 during theservicing thereof; and

FIG. 6 is an exploded perspective view of a portion of the replacementkeybar illustrated in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, specific preferred embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand that changes may be made without departing from the spirit and scopeof the present invention.

After periods of electrical power generator use, it may become necessaryto replace a stator core within a stator core frame of the powergenerator. As mentioned above, U.S. Pat. Nos. 7,302,754; 7,353,586; and7,395,594 are directed at installing stator cores into stator frameswithout placing the stator frame in an upright position. Typically, thesystems, structures, and methods disclosed by these patents are utilizedwith keybars having rounded engagement surfaces, i.e., the keybars aregenerally rounded in shape. This is because replacement of a stator coreonto rounded keybars using a horizontal replacement process is believedto be easier and more efficient as compared to replacement of a statorcore onto dove-tail shaped keybars.

As shown in FIG. 1, a power generator stator frame 10 may comprise amain housing 11 for supporting a stator core, not shown in FIG. 1. Themain housing 11 comprises an outer structure 13 and a main supportstructure 15 coupled to the outer structure 13. The main supportstructure 15 comprising a plurality of stator bore rings 18 fixedlycoupled to the outer structure 13 and a plurality of frame beams 16fixedly coupled to the stator bore rings 18. The main housing 11 furthercomprises a plurality of building bolts or keybars 12, which aredove-tail shaped in FIG. 1, and coupled to the frame beams 16. Thestator core, not shown in FIG. 1, is supported in the stator frame 10via the keybars 12.

In accordance with the present invention, after a stator core mounted todove-tail shaped keybars 12 of a stator frame 10 is removed, thedove-tail shaped keybars 12 are then removed and replaced with generallyrounded or cylindrical-shaped keybars followed by the installation of anew stator core onto the rounded keybars. By replacing the dove-tailshaped keybars 12 with rounded keybars, it is believed that installationof the new stator core within the stator core frame having roundedkeybars will be accomplished in a more efficient manner.

Donuts 14 mounted on dove-tail shaped keybars 12, see FIGS. 1-3, anddefining a stator core to be replaced, are removed according to anytraditional method(s) for removing such a stator core from acorresponding stator frame. For example, the stator core donuts 14 maybe individually removed one by one by axially sliding the stator coredonuts 14 along the dove-tail shaped keybars 12 until all stator coredonuts 14 are removed from the stator frame 10. It is noted that donuts14 comprise two or more stator core rings laminated together. Instead ofusing donuts 14 in the present invention, individual stator core ringsor laminations may be used instead.

Once the stator core donuts 14 are removed from the stator frame 10, thedove-tail shaped keybars 12 are removed from the frame beams 16 byremoving fasteners 22, such as bolts, extending through counter-boredholes 24 (see FIG. 3) formed in the keybars 12 and through correspondingholes 25 formed in the frame beams 16. Removing the fasteners 22 freeseach keybar 12 from its respective frame beam 16.

In order for a replacement donut 30 (see FIG. 4) to be more easilyinstalled in the stator frame 10 and in accordance with the presentinvention, one or more of the frame beams 16 are serviced by removingradially inner corner edges 16A₁, 16B₁ (see FIG. 3) of the frame beams16, such that the modified frame beams 16′ comprise beveled radiallyinner corner edges 16A₂, 16B₂ (see FIG. 5). The beveled radially innercorner edges 16A₂, 16B₂ provide an amount of radial clearance betweenthe frame beams 16′ and a radial outer edge 30A of each of thereplacement donuts 30. The beveled radially inner corner edges 16A₂,16B₂ may be formed in the frame beams 16′, for example, by grinding theradially inner corner edges 16A₁, 16B₁ using a portable milling machine(not shown), such as, for example, a TKF1500-0 model adjustable anglebeveller manufactured by Trumpf Inc. of Farmington, Conn.

Replacement building bolts or keybars 32 are then installed on the framebeams 16′ in generally the same locations as the previously removedkeybars 12. As shown in FIG. 5, the replacement keybars 32 are generallyrounded in shape and comprise a generally rounded engagement surface 34instead of the dove-tail shape of the removed keybars 12.

The replacement keybars 32 include counter-bored holes 36 formedtherein, as shown in FIGS. 5 and 6, which counter-bored holes 36 may besubstantially aligned with the holes 25 formed in the frame beams 16′,although it is understood that new holes (not shown) may be formed inthe frame beams 16′ and aligned with the counter-bored holes 36 in thereplacement keybars 32 if desired. Fasteners 38, depicted in FIGS. 5 and6 as bolts, are then inserted into the counter-bored holes 36 in thereplacement keybars 32 and threaded into the corresponding holes 25 inthe frame beams 16′ to secure the replacement keybars 32 to the framebeams 16′. The fasteners 38 may be inserted into the counter-bored holes36 until a radially inner surface 32A of the corresponding replacementkeybar 32 extends further radially inwardly than an end portion 38A ofeach of the fasteners 38, i.e., until the fasteners 38 are not extendingout past the radially inner surfaces 32A of the replacement keybars 32.Thus, the replacement donuts 30 can be axially slid on the replacementkeybars 32 without contacting the fasteners 38.

As shown in FIG. 5, the replacement donuts 30 include grooves 50. Eachreplacement donut 30 is positioned relative to the stator frame 10 suchthat each groove 50 is aligned with a corresponding replacement keybar32. Thereafter, the replacement donut 30 is horizontal moved into thestator frame such that the replacement keybars 32 are received in acorresponding one of the grooves 50 in the replacement donut 30. Thereplacement donuts 30 may be installed into the stator frame using thestructures and methods set out in U.S. Pat. Nos. 7,302,754, 7,353,586,and 7,395,594. Alternatively, any other suitable structures and methodscan be used to install the replacement donuts 30 into the stator frame10. A plurality of donuts 30 are installed in this fashion until apredetermined number have been installed so as to define a replacementstator core.

In the illustrated embodiment, the grooves 50 are slightly oversized toallow for easier installation of the donuts 30 onto the replacementkeybars 32. So as to create a tight fit between each donut 30 and thereplacement keybars 32, first and second wedge structure assemblies 54and 56 are provided in each groove 50 between the donut 30 and thecorresponding keybar 32, see FIG. 5. Each of the first and second wedgestructure assemblies 54, 56 in the embodiment shown comprises a fillermember 54A, 56A, and first and second wedges 54B, 54C and 56B, 56C. Inthe illustrated embodiment, six donuts 30, each having a width of aboutsix inches, are set in position. Thereafter, the first and second wedges54B, 54C and 56B, 56C and filler members 54A, 56A, each about 36 incheslong, are installed. The first and second wedge structure assemblies 54and 56 are utilized to aid in mounting the replacement donuts 30 on thereplacement keybars 32 and to secure a tight fit between the replacementdonuts 30 and the replacement keybars 32. It is understood that othertypes of mounting assist structures may be used as desired.

As noted above, the replacement of a stator core onto rounded keybarsusing a horizontal replacement process is believed to be easier and moreefficient as compared to replacement of a stator core onto dove-tailshaped keybars. Hence, replacing the dove-tail shaped keybars 12 withthe replacement keybars 32 facilitates an easier replacement of a statorcore within the stator frame 10. In particular, since tooling, methods,and structure have been developed to replace stator cores within statorframes using horizontal processes and cylindrical-shaped keybars, thesedeveloped tooling, methods, and structure can be utilized in the statorframes 10 once the replacement keybars 32 are installed. For example,the use of the replacement donuts 30 and the first and second wedgestructure assemblies 54, 56 with the replacement cylindrical-shapedkeybars 32 avoids developing new tooling, methods, and structure thatwould be required to use a horizontal process to replace a stator corein a stator frame that includes dove-tail shaped keybars.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A method of servicing a stator frame of a power generator comprising:removing a first stator core from a main housing of the stator frame;removing a plurality of first dove-tail shaped keybars that extendaxially within and are coupled to a main support structure forming partof the main housing; and installing a plurality of second keybars in themain support structure adapted to support a second stator core, each ofthe second keybars having a generally rounded engagement surface, thesecond stator core having recesses with shapes corresponding to thegenerally rounded engagement surfaces of the second keybars such thatthe second stator core can be securely supported by the main supportstructure via the second keybars.
 2. The method according to claim 1,wherein the main support structure comprises a plurality of stator borerings and a plurality of frame beams, the second keybars being coupledto the frame beams.
 3. The method according to claim 2, wherein saidstep of installing a plurality of second keybars in the main supportstructure comprises bolting the second keybars to the frame beams. 4.The method according to claim 3, wherein said step of bolting the secondkeybars to the frame beams comprises installing bolts into counter-boredholes formed in the second keybars.
 5. The method according to claim 3,further comprising installing the second stator core onto the secondkeybars.
 6. The method according to claim 5, wherein said step ofinstalling the bolts into counter-bored holes formed in the secondkeybars comprises installing the bolts into the counter-bored holesuntil end portions of the bolts are inserted past a radially innersurface of the second keybars.
 7. The method according to claim 2,further comprising servicing the frame beams such that the second statorcore can be more easily axially slid onto the second keybars without thesecond stator core contacting the frame beams.
 8. The method accordingto claim 7, wherein said step of servicing the frame beams comprisesremoving radially inner corner edges of the frame beams to create aradial clearance for a radial outer edge of the second stator core. 9.The method according to claim 8, wherein a portable milling machine isutilized to remove the radially inner corner edges of the frame beams.10. A kit for servicing a stator frame of a power generator, the statorframe having dove-tail keybars installed therein supporting a firststator core within a main support structure of a main housing, said kitcomprising: a plurality of second keybars each having a generallyrounded engagement surface and adapted to replace the dove-tail shapedkeybars installed in the main support structure, said second keybarsbeing adapted to support a second stator core in the main supportstructure, the second stator core having recesses with shapescorresponding to the generally rounded engagement surfaces of the secondkeybars; and fasteners to couple said second keybars to the main supportstructure of the main housing.
 11. The kit according to claim 10,wherein the main support structure comprises a plurality of stator borerings and a plurality of frame beams, said second keybars being coupledto said frame beams with said fasteners.
 12. The kit according to claim11, wherein said fasteners comprise bolts.
 13. The kit according toclaim 12, wherein said bolts are installed through counter-bored holesin said second keybars.
 14. The kit according to claim 13, wherein endportions of said second keybars extend further radially inwardly than aradial end of said bolts.
 15. The kit according to claim 10, furthercomprising a portable milling machine for removing radially inner corneredges of said frame beams to create a radial clearance for a radialouter edge of said second stator core.